Dual Radio Operation Between Access Systems Using 3gpp Radio Access Technology

1. An apparatus comprising processing circuitry configured to cause a user equipment (UE) to: determine to perform a handover between a first base station associated with a first network core and a second base station associated with a second network core, wherein the first base station corresponds to a first radio access technology (RAT), wherein the second base station corresponds to a second RAT different from the first RAT; in response to determining that the UE is to perform said handover: determine whether to retain an internet protocol (IP) address associated with the first network core or the second network core during handover; and transmit to the first base station or the second base station a message to establish a connection, the message comprising a request type, wherein the request type is determined based on whether or not IP address retention is to occur.

2. The apparatus of claim 1 , wherein the second base station is a booster node, wherein the first base station is an anchor node relative to the UE.

3. The apparatus of claim 1 , wherein the UE is connected to the second base station either before or after handover, wherein the second base station is a 5G standalone node, wherein the UE is free from being connected to the first network core either after or before the handover.

4. The apparatus of claim 1 , wherein the second base station is a 5G dual mode base station.

5. The apparatus of claim 1 , further comprising a plurality of radios configured according to different RATs, including the first RAT and the second RAT; wherein the processing circuitry is further configured to configure the UE to operate in a dual mode in which the UE is simultaneously connected with the first base station and the second base station.

6. The apparatus of claim 1 , wherein the processing circuitry is further configured to: configure the UE to operate in one of a connected mode or an idle mode with respect to the first network core; and independently configure the UE to operate in one of the connected mode or the idle mode with respect to the second network core.

7. The apparatus of claim 1 , wherein the processing circuitry is further configured to: in response to a determination that a new IP address is to be assigned during handover, cause a transceiver of the UE to transmit to one of the first base station or the second base station a second message comprising a request type that is free from an indication of handover.

8. The apparatus of claim 1 , wherein the processing circuitry comprises a baseband processor, wherein the apparatus further comprises a transceiver configured to communicate with at least one of the first base station or the second base station.

9. An apparatus of a mobility management node, the apparatus comprising processing circuitry configured to cause a mobility management node to: receive, from a user equipment (UE), a connection establishment message, wherein the connection establishment message is received via a first network core associated with a first base station or via a second network core associated with a second base station, wherein the first base station and the second base station correspond respectively to a first radio access technology (RAT) and a second RAT, wherein the connection establishment message comprises a request type that is selectable by the UE, wherein request type is used to determine whether or not Internet Protocol (IP) address retention is to occur in a handover between the first base station and second base station; perform the handover with or without IP address retention, according to the request type.

10. The apparatus of claim 9 , wherein the first network core is an Evolved Packet Core (EPC) of 3GPP Long Term Evolution (LTE).

11. The apparatus of claim 9 , wherein the second network core is a 5G core network.

12. The apparatus of claim 9 , wherein the first RAT is 3GPP Long Term Evolution (LTE), wherein the second RAT is 5G New Radio (NR).

13. The apparatus of claim 9 , wherein the second base station is a 5G standalone base station or a 5G dual mode base station.

14. A non-transitory memory medium storing program instructions, wherein the program instructions, when executed by processing circuitry, cause a user equipment (UE) to perform operations comprising: determining whether the UE is configured for handover between a first base station associated with a first network core and a second base station associated with a second network core, wherein the first base station corresponds to a first radio access technology (RAT), wherein the second base station corresponds to a second RAT different from the first RAT; in response to determining that the UE is configured for said handover: determining whether to retain an internet protocol (IP) address associated with the first network core or the second network core during handover; and transmitting to the first base station or the second base station a message to establish a connection, the message comprising a request type, wherein the request type is determined based on whether or not IP address retention is to occur.

15. The non-transitory memory medium of claim 14 , wherein a packet data network (PDN) connection is moved to the second RAT as part of the handover.

16. The non-transitory memory medium of claim 14 , wherein the first network core is an Evolved Packet Core (EPC) of 3GPP Long Term Evolution (LTE), wherein the second network core is a 5G core network, wherein the first RAT is 3GPP LTE, and wherein the second RAT is 5G New Radio (NR).

17. The non-transitory memory medium of claim 14 , wherein the first network core is a 5G core network, wherein the second network core is an Evolved Packet Core (EPC) of 3GPP Long Term Evolution (LTE), wherein the first RAT is 5G New Radio (NR), and wherein the second RAT is 3GPP LTE.

18. The non-transitory memory medium of claim 14 , wherein the UE is connected to the second base station either before or after handover, wherein the second base station is a 5G standalone node, wherein the UE is free from being connected to the first network core either after or before the handover.

19. The non-transitory memory medium of claim 14 , wherein the operations further comprise: configuring the UE to operate in a dual mode in which the UE is simultaneously connected with the first base station and the second base station.

20. The non-transitory memory medium of claim 14 , wherein the operations further comprise: configuring the UE to operate in one of a connected mode or an idle mode with respect to the first network core; and independently configuring the UE to operate in one of the connected mode or the idle mode with respect to the second network core.